U.S. patent application number 09/805688 was filed with the patent office on 2001-11-22 for composition and method for treating aqueous composition contaminants.
Invention is credited to Sivavec, Timothy Mark.
Application Number | 20010042723 09/805688 |
Document ID | / |
Family ID | 22976186 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042723 |
Kind Code |
A1 |
Sivavec, Timothy Mark |
November 22, 2001 |
Composition and method for treating aqueous composition
contaminants
Abstract
A non-iron sulfide is introduced into an iron-containing zone to
form ferrous sulfide. A contaminated aqueous composition is then
contacted with the ferrous sulfide to react with said
contaminants.
Inventors: |
Sivavec, Timothy Mark;
(Clifton Park, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY
CRD PATENT DOCKET ROOM 4A59
P O BOX 8
BUILDING K 1 SALAMONE
SCHENECTADY
NY
12301
US
|
Family ID: |
22976186 |
Appl. No.: |
09/805688 |
Filed: |
March 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09805688 |
Mar 13, 2001 |
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09257405 |
Feb 25, 1999 |
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6238570 |
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Current U.S.
Class: |
210/749 |
Current CPC
Class: |
Y10S 210/913 20130101;
C02F 2101/322 20130101; B09C 1/002 20130101; C02F 1/705 20130101;
G21F 9/06 20130101; C02F 2103/06 20130101; C02F 2101/36 20130101;
Y10S 210/912 20130101 |
Class at
Publication: |
210/749 |
International
Class: |
C02F 001/68 |
Claims
What is claimed is:
1. A method for treating an aqueous composition, comprising:
introducing a non-iron sulfide into an iron-containing zone to form
ferrous sulfide; and contacting a contaminated aqueous composition
with said ferrous sulfide.
2. The method of claim 1, wherein said aqueous composition is
contaminated with halogenated hydrocarbon and said sulfide is
mineralized to ferrous sulfide to react with and dehalogenate said
halogenated hydrocarbon.
3. The method of claim 2, wherein said halogenated hydrocarbon is a
chlorinated hydrocarbon and said ferrous sulfide dechlorinates said
chlorinated hydrocarbon to generate a reduced hydrocarbon and
chloride.
4. The method of claim 3, wherein said aqueous composition is
contaminated with at least one chlorinated hydrocarbon selected
from the group consisting of: tetrachloroethylene,
trichloroethylene, dichloroethylene, vinyl chloride,
trichloroethane, dichloroethane, chloroethane, carbon
tetrachloride, chloroform, dichloromethane, and chloromethane.
5. The method of claim 1, comprising introducing said non-iron
sulfide comprises: emplacing said sulfide into an environment
together with said iron; and contacting said aqueous composition in
said environment.
6. The method of claim 1 wherein the step of introducing said
non-iron sulfide comprises introducing a sulfide salt.
7. The method of claim 1, wherein the step of introducing said
non-iron sulfide comprises introducing at least one of sodium
sulfide, sodium hydrogen sulfide, or and hydrogen sulfide.
8. The method of claim 1, wherein the step of introducing the
non-iron sulfide comprises introducing as an aqueous solution into
a subsurface through an injection well.
9. The method of claim 1, wherein the step of introducing the
non-iron sulfide comprises introducing a polymer-coated sulfide to
provide a slow release composition for injection into said aqueous
composition.
10. The method of claim 1 wherein the aqueous composition comprises
a pH in a range between about 3 and about 11.
11. The method of claim 1 wherein the aqueous composition is
unbuffered.
12. The method of claim 1, further comprising the step of
controlling a pH of said aqueous composition by the addition of a
buffering agent.
13. The method of claim 12, wherein said pH is controlled within a
range of about 5 to about 9.
14. The method of claim 1, wherein the step of introducing the
non-iron sulfide comprises introducing a reductant to solubilize
ferrous ion from iron-bearing minerals, soils, sediments, or
aquifer materials.
15. The method of claim 14, wherein said reductant is an organic
acid or salt of an organic acid.
16. The method of claim 1, wherein said aqueous composition is a
groundwater composition.
17. The method of claim 1, wherein said aqueous composition
comprises an aquifer, moist soil, river sediment, or pond
sediment.
18. The method of claim 1, wherein a sulfide comprises introducing
by diffusion of said non-iron sulfide from a screened well.
19. The method of claim 18, wherein said non-iron sulfide comprises
sodium sulfide nonahydrate or anhydrous sodium sulfide.
20. The method of claim 1, wherein said aqueous composition
comprises an iron(III)-containing mineral.
21. The method of claim 20, wherein said iron(III)-containing
mineral is magnetite, goethite, hematite, maghemite, ferihydrite,
lepidocricite, or mixtures thereof.
22. The method of claim 2, further comprising the step of
contacting said non-iron sulfide with said aqueous composition in a
tower.
23. The method of claim 2, wherein said iron is admixed with an
inert filler.
24. The method of claim 23, wherein said inert filler comprises pea
gravel or coarse sand.
25. The method of claim 1, wherein said aqueous composition is
contaminated with oxidized metal or radionuclide and said non-iron
sulfide is mineralized to ferrous sulfide to react with and to
reduce said oxidized metal or radionuclide.
26. The method of claim 25, wherein said oxidized metal or
radionuclide comprises hexavalent chromium or hexavalent
uranium.
27. The method of claim 26, wherein said oxidized metal comprises
chromate.
28. The method of claim 26, wherein said radionuclide comprises
uranyl.
29. The method of claim 26, wherein said aqueous composition is
produced by the migration of groundwater through mine tailings.
30. The method of claim 25, wherein said aqueous composition is
further contaminated with halogenated hydrocarbon and said non-iron
sulfide is mineralized to ferrous sulfide to react with and
dehalogenate said halogenated hydrocarbon.
31. A method for treatment of an aqueous composition contaminated
with chlorinated hydrocarbon compounds, comprising injecting an
effective amount of non-iron sulfide with an iron-bearing mineral,
soil or aquifer material to mineralize ferrous sulfide to provide
reactive sites at which the chlorinated hydrocarbon compounds are
dechlorinated to reduced hydrocarbons and chloride.
32. A method of remediation of ground water contaminated with
halogenated hydrocarbon compounds, the method comprising: forming a
reactive zone comprising an effective amount of non-iron sulfide in
reactive contact with an iron-bearing mineral in the path of a
flowing plume of contaminated ground water; and allowing
contaminated ground water to pass through the reactive zone to
effect reductive dehalogenation of the halogenated hydrocarbon
compounds.
33. A method for treatment of an aqueous environment contaminated
with oxidized metal, radionuclide or mixtures of oxidized metal or
radionuclide contaminants, said method comprising; injecting an
effective amount of non-iron sulfide with an iron-bearing mineral,
soil, or aquifer material to mineralize ferrous sulfide to provide
reactive sites at which the oxidized metal or radionuclide is
reduced to a lower oxidation state.
34. A composition of matter, comprising a non-iron sulfide emplaced
with an iron-containing material in a reaction zone for contact
with a contaminated aqueous composition.
35. The composition of claim 34, wherein said non-iron sulfide is
emplaced with said iron-containing material in contact with said
contaminated aqueous composition.
36. The composition of claim 35, wherein said aqueous composition
is contaminated with a halogenated hydrocarbon.
37. The composition of claim 35, wherein said aqueous composition
is contaminated with at least one halogenated hydrocarbon, at least
one oxidized metal, at least one radionuclide, or mixtures
thereof.
38. The composition of claim 35, wherein said aqueous composition
is contaminated with an oxidized chromium-containing species.
39. The composition of claim 35, wherein said aqueous composition
is contaminated with at least one chlorinated hydrocarbon selected
from the group consisting of: tetrachloroethylene,
trichloroethylene, dichloroethylene, vinyl chloride,
trichloroethane, dichloroethane, chloroethane, carbon
tetrachloride, chloroform, dichloromethane, and chloromethane.
40. The composition of claim 35, wherein said non-iron sulfide
comprises a sulfide salt.
41. The composition of claim 35, wherein said non-iron sulfide
comprises sodium sulfide, sodium hydrogen sulfide or hydrogen
sulfide.
42. The composition of claim 35, wherein said non-iron sulfide
comprises polymer-coated to provide a slow release composition.
43. The composition of claim 35, wherein said halogenated
hydrocarbon is selected from the group consisting of:
trichloroethylene, dichloroethylene, and vinyl chloride.
44. The composition of claim 35, wherein the aqueous composition
has a pH in a range between about 3 and about 11.
45. The composition of claim 35, wherein the aqueous composition is
unbuffered.
46. The composition of claim 35, further comprising controlling a
pH of said aqueous composition by the addition of a buffering
agent.
47. The composition of claim 46, wherein said pH is controlled
within a range of about 5 to about 9.
48. The composition of claim 35, further comprising a reductant to
solubilize ferrous ion.
49. The composition of claim 48, wherein said reductant is an
organic acid or salt of an organic acid.
50. The composition of claim 35, wherein said aqueous composition
is a groundwater composition.
51. The composition of claim 35, wherein said aqueous composition
is derived from at least one of an aquifer, moist soil, river
sediment, or pond sediment.
52. The composition of claim 35, wherein said iron-containing
mineral comprises at least one of magnetite, goethite, hematite,
maghemite, ferihydrite, lepidocricite, or mixtures thereof.
53. The composition of claim 35, wherein said reaction zone
comprises a contact tower.
54. The composition of claim 35, wherein said iron admixed with an
inert filler.
55. The composition of claim 54, wherein said inert filler
comprises pea gravel or coarse sand.
56. The composition of claim 35, wherein said aqueous composition
is contaminated with oxidized metal or radionuclide, and said
sulfide is mineralized to ferrous sulfide to react with and to
reduce said oxidized metal or radionuclide.
57. The composition of claim 56, wherein said oxidized metal or
radionuclide comprises hexavalent chromium or hexavalent
uranium.
58. The composition of claim 56, wherein said oxidized metal is
chromate.
59. The composition of claim 56, wherein said radionuclide is
uranyl.
60. The composition of claim 56, wherein said aqueous composition
is further contaminated with halogenated hydrocarbon, and said
sulfide is mineralized to ferrous sulfide to react with and
dehalogenate said halogenated hydrocarbon.
61. The composition of claim 35, wherein said aqueous composition
is produced by the migration of groundwater through mine tailings.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for treating
aqueous composition contaminants. In particular, the invention
relates the treatment of aqueous compositions containing
contaminating halogenated hydrocarbons, oxidized metal species,
radionuclides, or mixtures thereof.
[0002] Halogenated hydrocarbons, particularly chlorinated
hydrocarbons, are excellent solvents for many applications. They
have low flammability and are fairly stable, both chemically and
biologically. They are commonly used in industry as chemical
carriers and solvents, paint removers and cleaners. The cleaning
applications include metal degreasing, circuit board cleaning,
metal parts cleaning and dry cleaning. Chlorinated solvents are
also used as intermediates in chemical manufacturing and as carrier
solvents for pesticides and herbicides.
[0003] Chlorinated hydrocarbons are very stable compounds and are
relatively toxic at low levels. Groundwaters have become
contaminated by chlorinated hydrocarbons from sources, such as
disposal facilities, chemical spills and leaking underground
storage tanks. Chlorinated solvents also may be released to the
environment through the use, loss, or disposal of a neat liquid, or
through the use or disposal of wash and rinse waters containing
residual solvents. Chlorinated solvents are among the most common
ground water contaminants because of their widespread use and
stability.
[0004] Subsurface movement and dispersion of chlorinated solvents
vary depending on whether the solvents are released as neat liquid
or in dissolved form. If released in dissolved form, chlorinated
solvent migration is governed largely by hydrogeological processes.
The presence of solubilizing agents, such as soaps (from wash
waters), counteracts natural soil sorption-retardation mechanisms
and facilitates the migration of the dissolved solvents. If the
chlorinated solvent is released as a neat liquid, the liquid
solvent migrates downwardly through a soil column under the force
of gravity. A portion of the solvent is retained in the soil pores.
If sufficient solvent is present, however, the soil pores become
saturated. Further, solvent then continues to move downwardly until
it encounters a physical barrier or the water table. If the solvent
encounters the water table, it spreads out until enough mass
accumulates to overcome capillary forces. At this point, the
greater density of the chlorinated solvent causes it to penetrate
the surface of the water table and to travel downwardly by gravity
until the mass of moving liquid is diminished by sorption or until
it encounters an aquitard.
[0005] In recent years, groundwater contamination by chlorinated
hydrocarbons from sources, such as disposal facilities, chemical
spills and leaking underground storage tanks, has become a
significant environmental problem. Many of these chlorinated
hydrocarbons are highly toxic and classified as carcinogens or
suspect carcinogens. Of particular concern are the chlorinated
ethylenes, such as trichloroethylene (TCE), tetrachloroethylene,
commonly known as perchloroethylene (PCE) and chlorinated ethanes,
such as 1,1,1-trichloroethane (TCA), which have been used as
degreasing agents in a variety of industrial applications. Although
the use of chlorinated degreasing agents was severely curtailed in
1976, improper storage and uncontrolled disposal practices resulted
in significant contamination to groundwater aquifers. Chlorinated
solvents are highly mobile in soils and aquifers, due to their high
water solubility (e.g., 1100 mg/L TCE at 25.degree. C.), and a need
exists for removal treatments them from groundwater.
[0006] Pump-and-treat is a commonly applied treatment scheme for
contaminated groundwater. The treatment usually involves
withdrawing contaminated water from a well, volatilizing the
contaminants in an air stripping tower, and adsorbing the vapor
phase contaminants onto granular activated carbon (GAC). There are
substantial limitations to pump-and-treat technology. The process
is inefficient and some sites can require treatment for many
decades.
[0007] It is known that chlorinated compounds can be degraded by
reductive dechlorination, that is, replacement of chlorine
substituents by hydrogen. Metallic elements, such as iron and zinc,
have been used to degrade chlorinated organic compounds. Several
systems have used iron metal to conduct reductive dechlorination of
hydrocarbons in aqueous compositions. Gillham, in U.S. Pat. No.
5,266,213, discloses feeding contaminated groundwater through a
trench containing an iron species. The process is conducted under
strict exclusion of oxygen over a lengthy period of time. Large
amounts of iron are needed for completion of the reactions.
Additionally, it is difficult to introduce large volumes of solid
reaction material, such as iron filings, into effective depths for
in situ remediation.
[0008] Sivavec, in U.S. Pat. No. 5,447,639, teaches a method for
enhanced remediation of aqueous solutions contaminated with
chlorinated aliphatic hydrocarbons. The method comprises reacting
reductively the chlorinated hydrocarbons with ferrous sulfide to
generate innocuous byproducts, such as ethane, ethene, and chloride
ion from chlorinated ethenes. Chlorinated aliphatic hydrocarbons,
including trichloroethylene (TCE), tetrachloroethylene, and
chlorinated ethanes such as 1,1,1-trichloroethane, are reduced to
ethene, ethane, and chloride ion (Cl.sup.-1) when contacted with
iron (II) sulfide under aerobic or anaerobic conditions. The
reaction may proceed, in situ or ex situ, by an electron transfer
mechanism at the mineral-water interface wherein ferrous ion
(Fe.sup.+2) and/or sulfide in ferrous sulfide function as reducing
agents and are oxidized to ferric ion (Fe.sup.+3) and sulfate
(SO.sub.4.sup.-2), respectively.
[0009] According to U.S. Pat. No. 5,447,639, an effective amount of
ferrous sulfide is admixed with a contaminated aqueous composition
to generate ethane, ethene, and chloride ion. Granular ferrous
sulfide may be filled into a pit, ditch, screened well or trench,
and used to react with and degrade chlorinated aliphatic compounds
in a migrating plume, such as groundwater aquifer and drainage
runoff. In another aspect, a tower column is packed with ferrous
sulfide. Industrial wastewater or pumped groundwater is then
treated in the tower. Additionally, an inert filler, such as sand,
gravel, pebbles, and the like, can be added to the ferrous sulfide
to increase its hydraulic conductivity. Polymeric adsorbents, such
as polyethylene, polypropylene, thermoplastic elastomers, and
carbon-filled rubbers, can also be admixed with the granular
ferrous sulfide.
[0010] Sivavec in U.S. Pat. No. 5,750,036 teaches a process for the
reductive dehalogenation of halogenated solvents by contact with
ferrous ion-modified clay minerals and iron (III)-containing soils,
sediments or aquifer materials. Examples of ferrous ion sources
include iron(II) sulfate heptahydrate, and the reductive
dissociation product of magnetite (Fe.sub.3O.sub.4) and oxalic
acid.
[0011] According to U.S. Pat. No. 5,750,036, ferrous ion is
introduced into clay minerals, clay bearing soils or sediments,
iron(III) minerals and iron(III)-bearing soils, or sediments by a
variety of methods. Examples of the methods include: (1) direct
treatment of contaminated material with ferrous ion in aqueous
solution; (2) dissolution of ferrous ion provided by the
interaction of iron-bearing minerals with organic and inorganic
reducing agents; (3) dissolution of ferrous ion resulting from iron
metal corrosion; (4) dissolution of ferrous ion formed by
electrolytic processes at iron electrodes; and (5) dissolution of
ferrous ion produced by stimulation and growth of iron-reducing
bacteria in iron-containing substrates such as soil sediment.
[0012] Lancy, in U.S. Pat. No. 3,294,680, discloses conditioning
spent cooling water that has a toxic hexavalent chromium solution
content. According to the method, a mass of hard metal sulfide
granules is provided and cooling water is moved through the mass in
contact with surface-reacting granules. The hexavalent chromium
solution content is converted to trivalent chromium.
[0013] There remains a need to effectively treat aqueous
compositions, particularly groundwater, that is contaminated with
chlorinated hydrocarbons, oxidized metal species, radionuclides, or
mixtures thereof.
SUMMARY OF THE INVENTION
[0014] The invention is a method for treating a contaminated
aqueous composition, such as groundwater. A non-iron sulfide is
introduced into an iron-containing zone to form ferrous sulfide. A
contaminated aqueous composition then contacts with the ferrous
sulfide. The aqueous composition may be contaminated with
halogenated hydrocarbon, oxidized metal species, radionuclides, or
mixtures thereof. The sulfide is mineralized to ferrous sulfide to
react with and dehalogenate halogenated hydrocarbon, and thus
reduces oxidized metal species and radionuclides.
[0015] In another aspect, the invention includes a composition of
matter that comprises a non-iron sulfide emplaced with an iron-
containing material in a reaction zone for contact with a
contaminated aqueous composition.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention relates to a method for treating
aqueous compositions to remove and destroy contaminants. Herein,
the term "aqueous composition" includes water environments,
particularly natural water environments, such as, but not limited
to, aquifers, particularly groundwater, and other subsurface
environments generally, and pond and stream sediments and dampened
soil. The invention also relates to the destruction of contaminants
from process or waste waters, particularly industrial waste waters,
as the waters are passed through columns or canisters packed with
reactive materials. Contaminants include, but are not limited to,
halogenated hydrocarbons, oxidized metals, and radionuclides.
[0017] One embodiment the present invention comprises a method for
the reductive dehalogenation of halogenated solvents by contact
with iron-bearing aquifer materials, soils, sediments, or clay
minerals modified by treatment with a sulfide species, other than
iron sulfide. Alternatively, reductive dehalogenation occurs
through contact with at least one iron (III)-containing mineral
modified by treatment with a sulfide species, other than iron
sulfide. Illustrative iron (III)-containing minerals include, but
are not limited to, magnetite, goethite, hematite, maghemite,
ferihydrite, and lepidocricite.
[0018] Sulfide alone is unreactive with halogenated hydrocarbons.
Sulfide reductive dehalogenation of halogenated hydrocarbons in the
presence of iron appears to proceed according to two mechanisms:
(1) the sulfide acts as a reductant to reduce iron(III)-containing
minerals, such as, but not limited to, magnetite, goethite and
lepidocricite to iron(II); and (2) the sulfide mineralizes with
iron(II) to generate ferrous sulfide. The chlorinated solvents
degradation may occur by a reductive dechlorination mechanism in
which carbon-chlorine bond reduction is coupled to the oxidation of
Fe(II) to Fe(III) at, for example, a clay-bound, ferrous-water
interface. For example, trichloroethylene (TCE), dichloroethylene
(DCE), and vinyl chloride (VC) are reduced to ethene, ethane,
ethyne, and chloride. DCE and VC are intermediate products of TCE,
but are subsequently reduced to ethene, ethane, ethyne, and
chloride.
[0019] The treatment method can be applied to treatment of water
contaminated with water-miscible or soluble-halogenated, organic
compounds. Chlorinated solvent is a common contaminant in aquifers
and subsurface water-containing environments. TCE, DCE, VC,
tetrachloroethylene, dichloroethane,. trichloroethane, carbon
tetrachloride, chloroform, dichloromethane, and chloromethane are
illustrative examples of contaminants. Other halogenated
hydrocarbon compounds that may be treated include chloroethane,
methyl chloride, brominated methanes, brominated ethanes,
brominated ethenes, fluorinated methanes, fluorinated ethanes,
fluorinated ethenes, fluorochloromethanes, fluorochloroethanes,
fluorochloroethenes, hydrofluorochlorocarbons, and
hydrofluorocarbons. The reduction process of the invention reduces
TCE, DCE, and VC to ethene, ethane, ethyne, and chloride. Lower
concentrations of C3, C4, C5, and C6 hydrocarbons are also
generated.
[0020] The invention has application for in-situ treatment of
groundwater contaminated with halogenated, particularly
chlorinated, solvents. Natural hydraulic gradients transport
contaminants to sulfide-treated mineralized zones, where
degradation of the contaminants occurs to remove them from the
flowing water. If the concentration of contaminants, groundwater
velocity, and rate of degradation are known or can be predicted,
injection of sulfide into an environment along with, or in the
presence of Fe(III), can mineralize a sufficient quantity of
ferrous sulfide that can completely degrade migrating contaminants.
The treatment of an aqueous environment contaminated with
halogenated, particularly chlorinated, hydrocarbon compounds,
comprises emplacing a non-iron sulfide with an iron-bearing
mineral, soil, or aquifer material to mineralize an effective
amount of ferrous sulfide within the environment to provide
reactive sites. The halogenated hydrocarbon compounds are
dehalogenated at the reactive sites to reduce hydrocarbons and
halide ions. An "effective amount" of ferrous sulfide means an
amount to reduce at least some halogenated aliphatic hydrocarbons
to ethane, ethene, and halide ions.
[0021] An iron-bearing mineral or soil can be emplaced along with
the non-iron sulfide. Further, in situ iron-bearing clays, soil, or
aquifer material can be modified by injected non-iron sulfide in
solution. Exemplary iron(III)-containing minerals include, but are
not limited to, magnetite, goethite, hematite, maghemite,
ferihydrite, and lepidocricite. Natural hydraulic gradients then
transport the organic contaminants to the modified clay zones,
where degradation of the contaminants occurs. The non-iron sulfide
can be introduced from an appropriate location, for example, from
an excavated trench. Injection wells may be used to pump aqueous
sulfide ion-containing compositions to great depths. The pumping
generates at at least one of strategically placed reactive zones,
permeable treatment for perimeter control of a contaminated site.
Migrating plumes of ground water contaminated with halogenated
hydrocarbons are intercepted by the implanted or created reactive
zones thereby stopping the flow of contaminants. Also, the non-iron
iron sulfide can be introduced into a substrate from a screened
well, such as a well that contains a sulfide salt as a solid
reagent. The migrating groundwater dissolves the sulfide salt
through the screened well and distributes it to clay-containing
areas to mineralize as ferrous sulfide. The non-iron sulfide salt
may also be polymer-coated, so as to provide a controlled slow
release of sulfide into the groundwater.
[0022] The process may be performed in an ex-situ column or
canister containing iron-bearing minerals, soils, or clays that
have been treated with non-iron sulfide, where applicable. In an ex
situ application, a column can be packed with the
iron(III)-containing species, such as, but not limited to, an iron
(III)-containing mineral including magnetite, goethite, hematite,
maghemite, ferihydrite, lepidocricite, or mixtures thereof. Aqueous
sulfide is then introduced into the column to generate ferrous
sulfide. Groundwater can then be passed through the column.
Alternatively, industrial wastewater can be directly passed through
the column for remediation. Column dimensions and water input flow
are selected to provide an adequate and optimal residence time to
degrade contaminants.
[0023] Alternatively, sulfide-modified clays can be prepared ex
situ by contacting excavated iron-bearing clays with non-iron
sulfide in aqueous solution. The modified clays may be covered in
geotextile fabric to facilitate handling and placement. Covered or
emplaced clays can then be used as landfill liners, soil covers, or
as-treatment zones in remediation processes, including, but not
limited to, electroosmotic processes. The non-iron sulfide can be
added in any convenient form, such as sodium sulfide. For example,
sodium sulfide comprises at least one of sodium sulfide nonahydrate
(Na.sub.2S.9H.sub.2O), anhydrous sodium sulfide (Na.sub.2S), sodium
hydrogen sulfide, and hydrogen sulfide.
[0024] An inert filler including, but not limited to, pebbles, pea
gravel, or coarse sand, can be admixed with iron-bearing mineral in
either an in situ or ex situ treatment to assure that groundwater
flow is not impeded when fines of ferrous sulfide are deposited.
The filler also serves to decrease the resistance of a closely
packed soil or aquifer material to groundwater flow.
[0025] The reaction of the invention can be buffered or unbuffered.
The pH range is in a range between about 3 and about 11 (inclusive)
for unbuffered reactions. The pH range is in a range between about
5 and about 9 (inclusive) for buffered reactions
[0026] Organic and inorganic reductants can be used to help
solubilize ferrous ion from iron-bearing soils, sediments, and
aquifer materials. Examples of organic reductants include, but are
not limited to, organic acids, such as formic acid, acetic acid,
propionic acid, malonic acid, oxalic acid, malic acid, ascorbic
acid, succinic acid, citric acid, lactic acid, and EDTA. Salts of
organic acids may also be used as organic reductants. Illustrative
examples of organic salts include, but are not limited to, sodium
formate, sodium acetate, sodium malonate, sodium oxalate, sodium
ascorbate, sodium lactate, sodium citrate and sodium
ethylenediaminetetraacetic acid.
[0027] In another embodiment of the invention, a treatment of
aqueous compositions contaminated with oxidized metal,
radionuclide, or mixtures of oxidized metal and radionuclide. The
aqueous compositions can be produced by the migration of
groundwater through exposed mine tailings. An effective amount of
non-iron sulfide is injected into an iron-bearing mineral, soil, or
clay to mineralize ferrous sulfide within the iron-containing
environment to provide reactive sites at which the oxidized metal
or radionuclide can be reduced to a lower oxidation state, for
example, a precipitated oxidation state. Examples of oxidized metal
or radionuclide include, but are not limited to, hexavalent
chromium and hexavalent uranium. The oxidized metal can be chromate
or other oxidized chromium-containing species. The radionuclide
comprise uranyl (UO.sub.2.sup.+2) and other oxidized
uranium-containing species.
[0028] The method may also be used to treat aqueous compositions
that are contaminated with a mixture comprising halogenated
hydrocarbons, and oxidized metal species, halogenated hydrocarbons
and radionuclides, or halogenated hydrocarbons oxidized metal
species, and radionuclides. An illustrative mixture contains a
halogenated hydrocarbon, an oxidized chromium species, and a
radionuclide, such as uranyl.
[0029] The invention is further illustrated by the following
examples. These examples are not meant to limit the invention in
any way. The measurements and values set forth below are
approximate.
EXAMPLE 1
[0030] Site soil (50.0 grams (g)) was added to each of eight 120
milliliter (mL) borosilicate glass vials. The soil comprised about
5.7% silt and clay, 18.4% fine to medium sand, 52.8% medium to
coarse sand, 20.6% coarse sand to gravel, and 2.4% >1/4 inch
gravel. Total iron content of the soil measured 0.21%.
Milli-Q.RTM.-filtered (filtration system by Millipore Corporation,
Bedford, Mass.) deionized water was filter-sterilized (0.2 .mu.m)
and sodium sulfide nonahydrate was added to provide a 50 millmole
(mM) solution. The pH of the solution measured 12.0. Measurement of
pH was conducted using a Ross Sure-Flow pH combination electrode,
standardized with pH 7 and 10 buffers. TCE was added to provide a
solution that analyzed as having about .0.885 milligrams per liter
(mg/L) TCE.
[0031] Three vials were filled to capacity with the soil and sodium
sulfide/TCE solution. Three control vials, which contained no soil,
were also filled to capacity with the same sodium sulfide/TCE
solution. Further, three vials were also filled to capacity with
the soil and sodium sulfide/TCE solution, after the pH of the
solution had been adjusted to pH 7 by the addition of 50% HCl.
Three control vials that contained no soil were also filled to
capacity with the same sodium sulfide/TCE solution at pH 7. Two
additional control vials were prepared, each containing 50.0 g soil
and 0.885 mg/L aqueous TCE and no sulfide amendment.
[0032] The fourteen vials were capped with Teflon-lined septa and
sealed with an aluminum crimp cap. The contents were mixed by
rotation on a jar mill set at 35 rpm. All experiments were
conducted at ambient temperature (approx. 25.degree. C.).
[0033] After 16 hour (h), 24 h and 48 h sample times, the vials in
each series were removed from the jar mill and the jar contents
were allowed to settle. Aqueous solution aliquots (5.0 mL) of the
were removed from vials at each sample time using a 10 mL gas-tight
syringe and positive nitrogen pressure using an 18 gauge, 1.5 in.
bevel-tipped needle. The water samples (each 5.0 mL) were sampled
on a Tekmar purge-and-trap concentrator (with autosampler)
interfaced with a gas chromatograph equipped with a flame
ionization detector (Tekmar ALS 2016 autosampler (method 8: US EPA
601/624); Tekmar 3000 purge-and-trap concentrator and Hewlett
Packard 5890 series 11 gas chromatograph). A Hewlett Packard HP-624
capillary column (30 meter (m) length, 0.53 millimeter (mm) inside
diameter (i.d.), 3 micrometer (.mu.m) film thickness) was used. The
following GC temperature program was used: 40.degree. C. for 5
minutes (min), 10.degree. C./min to 180.degree. C., 180.degree. C.
for 10 min. TCE, cis-DCE, 1,1-DCE and VC standards ranging from 1
microgram per liter (.mu.g/L) to 25,000 .mu.g/L were used to
calibrate the gas chromatograph-flame ionization detector (GC-FID)
response.
[0034] The aqueous phase was also analyzed for hydrocarbon gaseous
products by purge-and-trap GC-FID, using a second Tekmar
purge-and-trap concentrator interfaced with a gas chromatograph
equipped with a flame ionization detector (Tekmar ALS 2016
autosampler (method 8: US EPA 601/624); Tekmar 3000 purge-and-trap
concentrator and Hewlett Packard 5890 series 11 gas chromatograph).
A PLOT fused silica Al.sub.2O.sub.3/Na.sub.2SO.sub.4 analytical
column supplied by Chrompack, Inc. (50 m, 0.32 mm i.d., 0.45 mm
outside diameter (o.d.), 5 .mu.m film thickness) was used to
achieve separation of C1-C6 hydrocarbon gases. The following GC
temperature program was used: 75.degree. C. for 5 min, 20.degree.
C./min to 120.degree. C., 120.degree. C. for 30 min.
[0035] Samples of settled aqueous phase (5.0 mL) were withdrawn by
gas-tight syringe and loaded directly onto the Tekmar 2016
autosampler. Ethane, ethene, ethyne, propane, propane, and seven C4
hydrocarbons (isobutane, n-butane, trans-2-butene, 1butene,
isobutene, cis-2-butene and 1,3-butadiene) were calibrated from 1 %
mixtures in nitrogen (Scott Specialty Gases) using a direct
injection method. Ten volumes of the 1% gas mixtures (5 microliters
(.mu.L) to 500 .mu.L) were used to generate the twelve calibration
curves.
[0036] The results of the batch experiments are summarized below in
Tables 1 and 2. Table 1 provides the results of reductive
dechlorination of TCE with soil amended with sulfide at pH 12 (50.0
g soil, 50 mM sodium sulfide and 0.885 mg/L aqueous TCE). Table 2
provides the results of reductive dechlorination of TCE with soil
amended with sulfide at pH 7 (50.0 g soil, 50 mM sodium sulfide and
0.885 mg/L aqueous TCE). C/Co represents the ratio of measured
concentration to initial concentration.
1 TABLE 1 Ethane, ethene and Time [TCE] ethyne as h mg/L C/Co
equiv. TCE pH 0 0.885 1.000 -- 12.0 (TCE/soil/ sulfide 16 0.110
0.124 0.84 11.7 24 0.013 0.015 0.82 11.7 48 .001 .001 0.77 10.9 0
0.885 1.000 -- (TCE/sulfide control) 16 control 0.880 0.994 n.d. 24
control 0.869 0.982 n.d. 48 control 0.851 0.961 n.d. 48 0.855 0.966
n.d. (soil/TCE control
[0037] In the Tables, "n.d." means non-detected by purge-and-trap
GC-FID. Black precipitate, which was formed as a result of the
sulfide amendment of the soil, was analyzed by X-ray diffraction
(XRD) and its diffraction pattern matched that of ferrous
2 TABLE 2 Ethane, ethene and Time [TCE] ethyne as h mg/L C/Co
equiv. TCE pH 0 0.885 1.000 -- 7.2 (TCE/soil/ sulfide 16 0.080
0.090 0.93 7.4 24 0.009 0.010 0.85 7.4 48 <0.001 <0.001 0.88
7.5 0 0.885 1.000 -- (TCE/sulfide control) 16 control 0.876 0.950
n.d. 24 control 0.841 0.982 n.d. 48 control 0.803 0.907 n.d. 48
0.764 0.863 n.d. (soil/TCE control)
EXAMPLE 2
[0038] The following illustrates the method by which an
iron-bearing bearing soil have sulfide added thereto in a
soil-packed column, thus providing a reactive media that
reductively dechlorinates chlorniated solvents.
[0039] A 2.times.24 in. column containing 11 glass sampling paced
at 2 in. intervals along the length of the column was packed with
the following materials (in order from bottom to top); 1.5 in.
glass beads (3 mm diameter), 6 in. sand, 12.5 in. soil and 4 in.
sand. The soil used was identical to that of Example 1, except that
it was autoclaved three times at 120.degree. C. and 15 lb pressure
for 3 h with a rest period of 24 h between each autoclaving.
Approximately 1000 cc of soil were packed into the column. The
column was capped with Teflon end caps connected to 1/8 inch Teflon
tubing. The water flow direction was from column bottom to column
top. A Teflon piston pump (Fluid Metering, Inc.; ceramic liner and
piston) was used to pump water into the column at a set input flow
rate.
[0040] Sampling of the column was performed at the sample ports
fitted with Teflon septa and aluminum crimp caps into which 2 in.
sample needles with luer-lock connectors were placed. Each needle
tip at each sample port was permanently positioned into the center
of the column. Two-way luer-lock connectors were attached to each
needle. Sampling of the column was performed using gas-tight
syringes that fitted directly to the luer-lock fittings at each
port. The column was saturated with Milli-Q.RTM.-filtered water
(filter-sterilized (0.2 .mu.m)) by passing approximately 1 gallon
of water through the column at a flow rate of 2.2 mL/min. A 100 mM
sodium sulfide solution adjusted to pH 7.2 was introduced into the
column, also at a set flow rate of 2.2 mL/min. The soil was
darkened by the rapid precipitation of ferrous sulfide, as the
sulfide solution entered the soil zones of the column. Over a 72 h
period, in which 11.35 L of 100 mM sodium sulfide solution was
pumped through the column, the soil's color changed from a light
tan to black. Milli-.RTM.-filtered water was passed through the
column to remove residual sulfide in solution. A 1 mg/L aqueous
solution of TCE was introduced into the column at a flow rate of
0.05 mL/min.
[0041] Table 3 lists the cumulative column residence times for each
sampled port at input flow rate of 0.50 mL/min. The rate data in
Table 3 indicate a TCE dechlorination rate constant. The Table
shows steady-state concentrations of TCE and daughter products
measured in a soil column amended with sodium sulfide.
Concentrations were averaged over 65 pore volumes of groundwater
influent (influent flow rate was set at 0.050 mL/min).
3TABLE 3 cumulative inches residence ethane, ethene Column from
time in and ethyne as Sample column redox-active [TCE] [cis DCE]
[VC] equiv. TCE port bottom media zone, min mg/L mg/L mg/L consumed
effluent pH 1 2 sand -- 1.41 n.d. n.d. 0.00 7.3 2 4 sand -- 1.38
n.d. n.d. 0.00 7.3 3 6 sand -- 1.37 n.d. n.d. 0.00 7.4 4 8 soil 12
1.35 0.002 n.d. 0.08 7.5 5 10 soil 58 1.30 0.001 n.d. 0.15 7.5 6 12
soil 105 1.18 0.006 0.003 0.47 7.6 7 14 soil 152 1.11 0.009 0.004
0.60 7.5 8 16 soil 198 1.06 0.014 0.006 0.73 7.7 9 18 soil 245 0.96
0.020 0.005 0.77 7.7 10 20 soil 291 0.85 0.021 0.005 0.87 7.6 11 22
sand -- 0.84 0.018 0.004 0.62 7.6
[0042] Concentrations of TCE daughter products, cis-DCE, VC, and
fully reduced products (ethene, ethane, and ethyne) as equivalents
of TCE are also given in Table 3 with influent and effluent pH's
measured by a Ross Sure-Flow pH combination electrode.
[0043] The examples demonstrate that sulfide addition to soil
effects complete reduction dechlorination of TCE. Control reactions
show that no degradation of TCE takes place in the absence of
sulfide.
[0044] While various embodiments were disclosed herein, it will be
appreciated from the specification that various combinations of
elements, variations, and improvements therein may be made by those
skilled in the art, and are within the scope of the invention.
* * * * *